Vehicle stability is a primary consideration in the design of any vehicle. Vehicle stability is a concern for both three-wheel vehicles and four-wheel vehicles. A vehicle stabilization system must prevent the vehicle from overturning during operation, especially when the vehicle is negotiating a corner.
Three-wheel vehicles are more likely to experience stability problems during operation than four-wheel vehicles. The lack of a second front wheel leaves a three-wheel vehicle vulnerable to overturning when making a turn.
Three-wheel vehicles have, however, certain advantages as compared to four-wheel vehicles. Some of the biggest advantages include ease of maneuverability and a smaller turning radius. In addition, three-wheel vehicles are lighter and easier to transport than four-wheel vehicles.
In the last several years, specialized vehicles--electrically powered personal mobility vehicles ("scooter vehicles")--have been developed for use by elderly, infirm, and disabled persons. These scooter vehicles are small and lightweight, and can dramatically improve the style of life available to elderly, infirm, and disabled persons. These scooter vehicles provide such persons with a high degree of mobility independence that may not otherwise be available.
Suitable scooter vehicles for use by elderly, infirm, and disabled persons present unique design and manufacturing challenges. For example, an ideal scooter vehicle must be small and compact. Preferably, a scooter vehicle should have the capability of being broken down into a few parts so that it can be transported, for example, inside the trunk of an automobile. An ideal scooter vehicle should also be lightweight to enable the user to lift, position, and manually move the scooter vehicle with little physical effort. An ideal scooter vehicle must further be powerful enough to travel up hills while maintaining a certain minimum speed, yet must be geared to move slowly and controllably down hills. Moreover, a preferred scooter vehicle must be designed to remain stable at all times when in operation. There are still other design requirements, beyond those described above, that are uniquely tied to a suitable electrically powered scooter vehicle.
Maintaining vehicle stability during all phases of scooter vehicle operation is a constant design challenge, particularly with respect to three-wheel scooter vehicles. A three-wheel scooter vehicle is more apt to tip over when maneuvering through a turn than a four-wheel scooter vehicle.
When a scooter vehicle is turning, similar to any vehicle, an overturning moment or force is generated which causes the vehicle to lean toward the outside of the turn. Another potential tipping situation occurs when the vehicle is traveling along or traversing the side of a hill, with the overturning force urging the vehicle to tip toward the downhill side. In either situation, the overturning force increases in magnitude as the speed of the vehicle increases. In addition, the higher the profile of the load on the scooter vehicle, the greater the magnitude of the overturning moment. Furthermore, the attitude of the vehicle will also have an effect on the overturning force experienced by the vehicle. If this overturning force becomes too great, the vehicle will tip about an axis formed between the front wheel and the rear wheel at the outside of the turn.
Training wheel-like devices have been developed to prevent three-wheel scooter vehicles from tipping over when they experience a sufficiently strong overturning force during a turn. Known training wheel-like devices are rigidly mounted to the front of the vehicle on each side of the main front wheel in fixed, constantly extended positions.
These known training wheel-like devices function essentially the same as training wheels on a bicycle. When the scooter vehicle experiences a tipping force of sufficient magnitude, the vehicle tips to one side and the weight of the vehicle becomes partially borne by the training wheel to prevent the vehicle from completely tipping over. After the turn is completed, the vehicle will rock back with the front vehicle tire resuming its role to bear all of the vehicle's forward weight.
Known training wheel-type devices have, however, several drawbacks. Because they are rigidly affixed to the scooter, they constantly remain in a downward extended position. As such, the training wheel legs provide little clearance between the bottom of the training wheel and the top of the ground. The constantly extended training wheels continually hit objects, even relatively low profile objects, in the path of the scooter vehicle.
Thus, there is a need to develop a stabilization device for scooter vehicles that will overcome the above described problems with respect to vehicle tipping, yet that will avoid the interference problems presented by the training wheel-type devices described above. The present invention overcomes the foregoing problems by providing an automatically deployable vehicle stabilization system which becomes effective only when the vehicle is turning. The various features, advantages, and objects of the invention will become apparent from the detailed disclosure that follows.